To determine the cost of each additional hour of parking, we can break down Jillian's parking expense as follows:
- The base rate for the first two hours is $3.
- Jillian parked for a total of 6 hours, meaning she parked for 4 additional hours beyond the initial 2 hours.
Let \( x \) be the cost of each additional hour of parking. The total cost can be expressed as:
\[ \text{Total cost} = \text{Base rate} + (\text{Additional hours} \times \text{Cost per additional hour}) \]
Substituting the known values:
\[ 31 = 3 + (4 \times x) \]
Now, simplify the equation:
\[ 31 - 3 = 4x \] \[ 28 = 4x \]
Next, divide both sides by 4:
\[ x = \frac{28}{4} = 7 \]
Thus, the cost of each additional hour of parking is $7.